wdiff draft-ietf-ospf-te-link-attr-reuse-06.txt draft-ietf-ospf-te-link-attr-reuse-07.txt

LSR Working Group P. Psenak, Ed.
Internet-Draft Cisco Systems, Inc. L. Ginsberg
Intended status: Standards Track A. Lindem Cisco Systems
Expires: May October 13, 2019 L. Ginsberg
Cisco Systems W. Henderickx
Nokia
J. Tantsura
Nuage Networks
H. Gredler
RtBrick Inc.
Apstra
J. Drake
Juniper Networks
November 9, 2018
April 11, 2019

OSPF Link Traffic Engineering (TE) Attribute Reuse
draft-ietf-ospf-te-link-attr-reuse-06.txt
draft-ietf-ospf-te-link-attr-reuse-07.txt

Abstract

Various link attributes have been defined in OSPF in the context of
the MPLS Traffic Engineering (TE) and GMPLS. Many of these link
attributes can be used for applications other than MPLS Traffic
Engineering or GMPLS. This document defines how to distribute such
attributes in OSPFv2 and OSPFv3 for applications other than MPLS
Traffic Engineering or GMPLS.

Status of This Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

This Internet-Draft will expire on May October 13, 2019.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements notation . . . . . . . . . . . . . . . . . . 4 3
2. Link attributes examples . . . . . . . . . . . . . . . . . . 4
3. Advertising Advertisement of Link Attributes . . . . . . . . . . . . . . . . . 4
3.1. OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA . . . . 4
3.2. 3
2.1. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA . 5
3.3. Selected Approach . . . . . . . . . . . . 4
3. Advertisement of Application Specific Values . . . . . . . . 6 5
4. Reused TE link attributes . . . . . . . . . . . . . . . . . . 6 8
4.1. Shared Risk Link Group (SRLG) . . . . . . . . . . . . . . 6 8
4.2. Extended Metrics . . . . . . . . . . . . . . . . . . . . 7 8
4.3. Traffic Engineering Metric Administrative Group . . . . . . . . . . . . . . . 8
4.4. Administrative Group . . . 9
4.4. Traffic Engineering Metric . . . . . . . . . . . . . . . 8 9
5. Advertisement of Application Specific Values . . . . . . . . 8
6. Maximum Link Bandwidth . . . . . . . . . . . . . . . . . . . 11
7. 10
6. Local Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 12
8. 10
7. Remote Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 12
9. 10
8. Deployment Considerations . . . . . . . . . . . . . . . . . . 12
10. 11
9. Attribute Advertisements and Enablement . . . . . . . . . . . 13
11. 11
10. Backward Compatibility . . . . . . . . . . . . . . . . . . . 14
12. 12
11. Security Considerations . . . . . . . . . . . . . . . . . . . 14
13. 12
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
13.1. 13
12.1. OSPFv2 . . . . . . . . . . . . . . . . . . . . . . . . . 14
13.2. 13
12.2. OSPFv3 . . . . . . . . . . . . . . . . . . . . . . . . . 15 13
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 14
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 15
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 15
15.1. Normative References . . . . . . . . . . . . . . . . . . 16 15
15.2. Informative References . . . . . . . . . . . . . . . . . 17 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18

1. Introduction

Various link attributes have been defined in OSPFv2 [RFC2328] and
OSPFv3 [RFC5340] in the context of the MPLS traffic engineering and
GMPLS. All these attributes are distributed by OSPFv2 as sub-TLVs of
the Link-TLV advertised in the OSPFv2 TE Opaque LSA [RFC3630]. In
OSPFv3, they are distributed as sub-TLVs of the Link-TLV advertised
in the OSPFv3 Intra-Area-TE-LSA as defined in [RFC5329].

Many of these link attributes are useful outside of traditional MPLS
Traffic Engineering or GMPLS. This brings its own set of problems,
in particular how to distribute these link attributes in OSPFv2 and
OSPFv3 when MPLS TE and GMPLS are not deployed or are deployed in
parallel with other applications that use these link attributes.

[RFC7855] discusses use cases/requirements for SR. Segment Routing.
Included among these use cases is SRTE. If both RSVP-TE and SRTE are
deployed in a network, link attribute advertisements can be used by
one or both of these applications. As there is no requirement for
the link attributes advertised on a given link used by SRTE to be
identical to the link attributes advertised on that same link used by
RSVP-TE, there is a clear requirement to indicate independently which
link attribute advertisements are to be used by each application.

As the number of applications which may wish to utilize link
attributes may grow in the future, an additional requirement is that
the extensions defined allow the association of additional
applications to link attributes without altering the format of the
advertisements or introducing new backwards compatibility issues.

Finally, there may still be many cases where a single attribute value
can be shared among multiple applications, so the solution should
minimize advertising duplicate link/attribute when possible.

1.1. Requirements notation

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].

2. Advertisement of Link attributes examples Attributes

This section lists some of outlines the solution for advertising link attributes
originally defined for MPLS Traffic Engineering that can be or GMPLS when they
are used for other applications in applications.

2.1. OSPFv2 Extended Link Opaque LSA and OSPFv3. The list doesn't necessarily contain all the
required attributes.

1. Remote Interface IP address [RFC3630] - OSPFv2 currently cannot
distinguish between parallel links between two OSPFv3 E-Router-LSA

Extended Link Opaque LSAs as defined in [RFC7684] for OSPFv2 routers.
As a result, the two-way connectivity check performed during SPF
may succeed when the two routers disagree on which of the links
to use for data traffic.

2. Link Local/Remote Identifiers - [RFC4203] - Used for the two-way
connectivity check for parallel unnumbered links. Also used for
identifying adjacencies and
Extended Router-LSAs [RFC8362] for unnumbered links in Segment Routing
traffic engineering.

3. Shared Risk Link Group (SRLG) [RFC4203] - In IPFRR, the SRLG is OSPFv3 are used to compute diverse backup paths [RFC5714].

4. Unidirectional Link Delay/Loss Metrics [RFC7471] - Could be used
for the shortest path first (SPF) computation using alternate
metrics within an OSPF area.

3. Advertising Link Attributes

This section outlines possible approaches for advertising advertise link
attributes originally defined for MPLS Traffic Engineering or GMPLS
when they that are used for by applications other applications.

3.1. OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA

One approach for advertising link attributes is to continue to use
the OSPFv2 TE Opaque LSA [RFC3630] then MPLS traffic
engineering or GMPLS. These LSAs were defined as a generic
containers for distribution of the OSPFv3 Intra-Area-TE-LSA
[RFC5329]. extended link attributes. There
are several problems with this approach:

1. Whenever the link is advertised in an OSPFv2 TE Opaque LSA or advantages in
an OSPFv3 Intra-Area-TE-LSA, the link becomes a part using them:

1. Advertisement of the TE
topology, which may link attributes does not match IP routed topology. By making make the link part
of the TE topology, remote nodes may mistakenly believe
that the link is available for MPLS TE or GMPLS, when, in fact,
MPLS topology. It avoids any conflicts and is not enabled on the link. fully
compatible with [RFC3630] and [RFC5329].

2. The OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA advertise
link attributes that remains
truly opaque to OSPFv2 and OSPFv3 as originally defined in
[RFC3630] and [RFC5329] respectively. Their contents are not used or required
inspected by MPLS TE or
GMPLS. OSPF, that acts as a pure transport.

3. There is no mechanism in these clear distinction between link attributes used by TE LSAs to indicate which
of the link attributes are passed to the MPLS TE application and
which are used by other applications including OSPF itself.

3. Link attributes used for non-TE applications are partitioned
across multiple LSAs - the TE Opaque LSA and the Extended Link
Opaque LSA in OSPFv2 and the OSPFv3 Intra-Area-TE-LSA and OSPFv3
Extended LSA Router-Link TLV [RFC8362] in OSPFv3. This
partitioning will require implementations to lookup multiple LSAs
to extract link attributes for a single link, bringing needless
complexity to OSPF implementations.

The advantage of this approach is that there is no additional
standardization requirement to advertise the TE/GMPL attributes for
other applications. Additionally, link attributes are only
advertised once when both OSPF TE and other applications are deployed
on the same link. This is not expected to be a common deployment
scenario.

3.2. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA

An alternative approach for advertising link attributes is to use
Extended Link Opaque LSAs as defined in [RFC7684] for OSPFv2 and
Extended Router-LSAs [RFC8362] for OSPFv3. These LSAs were defined
as a generic containers for distribution of the extended link
attributes. There are several advantages in using them:

1. Advertisement of the link attributes does not make the link part
of the TE topology. It avoids any conflicts and is fully
compatible with the [RFC3630] and [RFC5329].

2. The OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA remains
truly opaque to OSPFv2 and OSPFv3 as originally defined in
[RFC3630] and [RFC5329] respectively. Their contents are not
inspected by OSPF, that act as a pure transport.

3. There is clear distinction between link attributes used by TE and and
link attributes used by other OSPFv2 or OSPFv3 applications.

4. All link attributes that are used by other applications are
advertised in a single LSA, the Extended Link Opaque LSA in
OSPFv2 or the OSPFv3 E-Router-LSA [RFC8362] in OSPFv3.

The disadvantage of this approach is that in rare cases, the same
link attribute is advertised in both the TE Opaque and Extended Link
Attribute LSAs in OSPFv2 or the Intra-Area-TE-LSA and E-Router-LSA in
OSPFv3. Additionally, there will be additional standardization
effort. However, this could also be viewed as an advantage as the
non-TE use cases for the TE link attributes are documented and
validated by the LSR working group.

3.3. Selected Approach

It is RECOMMENDED to use the Extended Link Opaque LSA [RFC7684] and
E-Router-LSA [RFC8362] to advertise any link attributes used for non-
TE applications in OSPFv2 or OSPFv3 respectively, including those
that have been originally defined for TE applications.

It is also RECOMMENDED that TE link attributes used for RSVP-TE/GMPLS
continue to use OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area-
TE-LSA [RFC5329].

It is also RECOMMENDED to keep the

The format of the link attribute TLVs that have been defined for TE
applications will be kept unchanged even when they are used for non-TE non-
TE applications.

Finally, it is RECOMMENDED to allocate unique Unique code points will be allocated for these TE
link attribute TLVs in from the OSPFv2 Extended Link TLV Sub-TLV
Registry [RFC7684] and in from the OSPFv3 Extended LSA Sub-TLV Registry

[RFC8362]. For each reused TLV, the code point will be defined in an
IETF document along with the expected use-case(s).

4. Reused TE link attributes

This section defines the use case and code points for the OSPFv2
Extended Link TLV Sub-TLV Registry and OSPFv3 Extended LSA Sub-TLV
Registry for some

3. Advertisement of Application Specific Values

To allow advertisement of the link attributes that have been originally
defined for TE or GMPLS.

Remote interface IP address and Link Local/Remote Identifiers have
been added as sub-TLVs application specific values of OSPFv2 Extended Link TLV by [RFC8379].
Link Local/Remote Identifiers are already included in the OSPFv3
Router-Link TLV [RFC8362].

4.1. Shared Risk link
attribute, a new Application Specific Link Group (SRLG) Attributes (ASLA) sub-TLV
is defined. The SRLG of a link can be used in IPFRR to compute ASLA sub-TLV is a backup path that
does not share any SRLG group with the protected link.

To advertise the SRLG sub-TLV of the link in the OSPFv2 Extended
Link TLV,
the same format for the sub-TLV defined in section 1.3 of [RFC4203]
is used and TLV type TBD1 is used. Similarly, for OSPFv3 to
advertise the SRLG in the [RFC7471] and OSPFv3 Router-Link TLV, TLV type TBD2 [RFC8362].

The ASLA sub-TLV is
used.

4.2. Extended Metrics

[RFC3630] defines several link bandwidth types. [RFC7471] defines
extended link metrics that are based on link bandwidth, delay an optional sub-TLV and
loss characteristics. All these can be used to compute best paths
within an OSPF area to satisfy requirements for bandwidth, delay
(nominal or worst case) or loss.

To advertise extended link metrics appear multiple times
in the OSPFv2 Extended Link TLV,
the same format for the sub-TLVs defined in [RFC7471] is used with
the following TLV types:

TBD3 - Unidirectional Link Delay

TBD4 - Min/Max Unidirectional Link Delay

TBD5 - Unidirectional Delay Variation

TBD6 - Unidirectional Link Loss

TBD7 - Unidirectional Residual Bandwidth

TBD8 - Unidirectional Available Bandwidth

TBD9 - Unidirectional Utilized Bandwidth

To advertise extended link metrics in the OSPFv3 Extended LSA Router-
Link TLV, the same format for the sub-TLVs defined in [RFC7471] is
used with the following TLV types:

TBD10 - Unidirectional Link Delay

TBD11 - Min/Max Unidirectional Link Delay

TBD12 - Unidirectional Delay Variation

TBD13 - Unidirectional Link Loss

TBD14 - Unidirectional Residual Bandwidth

TBD15 - Unidirectional Available Bandwidth

TBD16 - Unidirectional Utilized Bandwidth

4.3. Traffic Engineering Metric

[RFC3630] defines Traffic Engineering Metric.

To advertise the Traffic Engineering Metric in the OSPFv2 Extended
Link TLV, the same format for the sub-TLV defined in section 2.5.5 of
[RFC3630] is used and TLV type TBD27 is used. Similarly, for OSPFv3
to advertise the Traffic Engineering Metric in the OSPFv3 Router-Link
TLV, TLV type TBD28 is used.

4.4. Administrative Group

[RFC3630] and [RFC7308] define the Administrative Group and Extended
Administrative Group sub-TLVs respectively.

One use case where advertisement of the Extended Administrative
Group(s) for a link is required is described in
[I-D.ietf-lsr-flex-algo].

To advertise the Administrative Group and Extended Administrative
Group in the OSPFv2 Extended Link TLV, the same format for the sub-
TLVs defined in [RFC3630] and [RFC7308] is used with the following
TLV types:

TBD17 - Administrative Group

TBD18 - Extended Administrative Group

To advertise Administrative Group and Extended Administrative Group
in the OSPFv3 Router-Link TLV, the same format for the sub-TLVs
defined in [RFC3630] and [RFC7308] is used with the following TLV
types:

TBD19 - Administrative Group

TBD20 - Extended Administrative Group

5. Advertisement of Application Specific Values

Multiple applications can utilize link attributes that are advertised
by OSPF. Some examples of applications using the link attributes are
Segment Routing Traffic Engineering and LFA [RFC5286].

In some cases the link attribute MAY have different values for
different applications. An example could be SRLG [Section 4.1],
where values used by LFA could be different then the values used by
Segment Routing Traffic Engineering.

To allow advertisement of the application specific values of the link
attribute, a new Application Specific Link Attributes (ASLA) sub-TLV
is defined. The ASLA sub-TLV is a sub-TLV of the OSPFv2 Extended
Link TLV [RFC7471] and OSPFv3 Router-Link TLV [RFC8362]. The ASLA
sub-TLV is an optional sub-TLV and can appear multiple times in the
OSPFv2 Extended Link TLV and OSPFv3 Router-Link TLV. It has TLV and OSPFv3 Router-Link TLV. It has
the following format:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SABML | UDABML | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Standard Application Bit-Mask |
+- -+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| User Defined Application Bit-Mask |
+- -+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Attribute sub-sub-TLVs |
+- -+
| ... |

where:

Type: TBD21 10 (OSPFv2), TBD22 TBD1 (OSPFv3)

Length: variable

SABML: Standard Application Bit-Mask Length. It MUST be a
multiple of 4 bytes. If the Standard Application Bit-Mask is not
present, the Standard Application Bit-Mask Length MUST be set to
0.

UDABML: User Defined Application Bit-Mask Length. It MUST be a
multiple of 4 bytes. If the User Defined Application Bit-Mask is
not present, the User Defined Application Bit-Mask Length MUST be
set to 0.

Standard Application Bit-Mask: Optional set of bits, where each
bit represents a single standard application. Bits are defined in
[I-D.ietf-isis-te-app], which also request a new IANA "Link
Attribute Applications" registry under "Interior Gateway Protocol
(IGP) Parameters" for them. The bits are repeated here for
informational purpose:

Bit-0: RSVP Traffic Engineering

Bit-1: Segment Routing Traffic Engineering

Bit-2: Loop Free Alternate (LFA). Includes all LFA types

Bit-3: Flexible Algorithm

User Defined Application Bit-Mask: Optional set of bits, where
each bit represents a single user defined application.

Standard Application Bits are defined/sent starting with Bit 0.
Additional bit definitions that are defined in the future SHOULD be
assigned in ascending bit order so as to minimize the number of
octets that will need to be transmitted.

User Defined Application bits have no relationship to Standard
Application bits and are NOT managed by IANA or any other standards
body. It is recommended that bits are used starting with Bit 0 so as
to minimize the number of octets required to advertise all of them.

Undefined bits in both Bit-Masks MUST be transmitted as 0 and MUST be
ignored on receipt. Bits that MUST be
ignored on receipt. Bits that are NOT transmitted MUST be treated as
if they are set to 0 on receipt.

If the link attribute advertisement is limited to be used by a
specific set of applications, corresponding Bit-Masks MUST be present
and application specific bit(s) MUST be set for all applications that
use the link attributes advertised in the ASLA sub-TLV.

Application Bit-Masks apply to all link attributes that support
application specific values and are advertised in the ASLA sub-TLV.

The advantage of not making the Application Bit-Masks part of the
attribute advertisement itself is that we can keep the format of the
link attributes that have been defined previously and reuse the same
format when advertising them in the ASLA sub-TLV.

When neither the Standard Application Bits nor the User Defined
Application bits are set (i.e., both SABML and UDABML are NOT transmitted 0) in the
ASLA sub-TLV, then the link attributes included in it MUST be treated
considered as
if they are set being applicable to 0 on receipt.

If all applications.

If, however, another advertisement of the same link attribute
includes any Application Bit-Mask in the ASLA sub-TLV, applications
that are listed in the Application Bit-Masks of such ASLA sub-TLV
SHOULD use the attribute advertisement is limited to be used by a which has the application
specific bit set of applications, corresponding in the Application Bit-Masks.

If the same application is listed in the Application Bit-Masks MUST be present
and of
more then one ASLA sub-TLV, the application specific bit(s) MUST be set for all applications that SHOULD use the first
advertisement and ignore any subsequent advertisements of the same
attribute. This situation SHOULD be logged as an error.

This document defines the initial set of link attributes that MUST
use ASLA sub-TLV if advertised in the OSPFv2 Extended Link TLV or in
the OSPFv3 Router-Link TLV. If the ASLA sub-TLV.

Application Bit-Masks apply to all sub-TLV includes any link
attribute(s) NOT listed below, they MUST be ignored. Documents which
define new link attributes that MUST state whether the new attributes
support application specific values and are as such MUST be advertised in the
an ASLA sub-TLV. The advantage of not making the Application Bit-Masks part of link attributes that MUST be advertised in ASLA
sub-TLVs are:

- Shared Risk Link Group

- Unidirectional Link Delay

- Min/Max Unidirectional Link Delay

- Unidirectional Delay Variation

- Unidirectional Link Loss

- Unidirectional Residual Bandwidth

- Unidirectional Available Bandwidth

- Unidirectional Utilized Bandwidth

- Administrative Group

- Extended Administrative Group

- Traffic Engineering Metric

4. Reused TE link attributes

This section defines the
attribute advertisement itself is that we can keep use case and code points from the format OSPFv2
Extended Link TLV Sub-TLV Registry and OSPFv3 Extended LSA Sub-TLV
Registry for some of the link attributes that have been originally
defined previously and reuse the same
format when advertising them in the ASLA sub-TLV.

When neither the Standard Application Bits nor the User Defined
Application bits are set (i.e., both SABML and UDABML are 0) in the
ASLA sub-TLV, then the for TE or GMPLS.

4.1. Shared Risk Link Group (SRLG)

The SRLG of a link attributes included in it MUST can be
considered as being applicable used in OSPF calculated IPFRR [RFC5714] to all applications.

If, however, another advertisement of the same link attribute
includes
compute a backup path that does not share any Application Bit-Mask in SRLG group with the ASLA sub-TLV, applications
that are listed in
protected link.

To advertise the Application Bit-Masks SRLG of such ASLA sub-TLV
SHOULD use the attribute advertisement which has the application
specific bit set link in the Application Bit-Masks.

If OSPFv2 Extended Link TLV,
the same application is listed in format for the Application Bit-Masks sub-TLV defined in section 1.3 of
more then one ASLA sub-TLV, the application SHOULD use the first
advertisement [RFC4203]
is used and ignore any subsequent advertisements of TLV type 11 is used. Similarly, for OSPFv3 to advertise
the same
attribute. This situation SHOULD SRLG in the OSPFv3 Router-Link TLV, TLV type TBD2 is used.

4.2. Extended Metrics

[RFC3630] defines several link bandwidth types. [RFC7471] defines
extended link metrics that are based on link bandwidth, delay and
loss characteristics. All these can be logged as used to compute primary and
backup paths within an error.

This document defines the initial set of OSPF area to satisfy requirements for
bandwidth, delay (nominal or worst case) or loss.

To advertise extended link attributes that MUST
use ASLA sub-TLV if advertised metrics in the OSPFv2 Extended Link TLV,
the same format for the sub-TLVs defined in [RFC7471] is used with
the following TLV or types:

12 - Unidirectional Link Delay

13 - Min/Max Unidirectional Link Delay

14 - Unidirectional Delay Variation

15 - Unidirectional Link Loss

16 - Unidirectional Residual Bandwidth

17 - Unidirectional Available Bandwidth

18 - Unidirectional Utilized Bandwidth

To advertise extended link metrics in the OSPFv3 Router-Link TLV. If Extended LSA Router-
Link TLV, the ASLA sub-TLV includes any link
attribute(s) NOT listed below, they MUST be ignored. Documents which
define new link attributes MUST state whether same format for the new attributes
support application specific values and as such MUST be advertised in
an ASLA sub-TLV. The link attributes that MUST be advertised in ASLA sub-TLVs are:

- Shared Risk Link Group defined in [RFC7471] is
used with the following TLV types:

TBD3 - Unidirectional Link Delay

TBD4 - Min/Max Unidirectional Link Delay

TBD5 - Unidirectional Delay Variation

TBD6 - Unidirectional Link Loss

TBD7 - Unidirectional Residual Bandwidth

TBD8 - Unidirectional Available Bandwidth

TBD9 - Unidirectional Utilized Bandwidth

4.3. Administrative Group

[RFC3630] and [RFC7308] define the Administrative Group and Extended
Administrative Group sub-TLVs respectively.

One use case where advertisement of the Extended Administrative
Group(s) for a link is required is described in
[I-D.ietf-lsr-flex-algo].

19 - Administrative Group

20 - Extended Administrative Group

TBD10 - Administrative Group

TBD11 - Extended Administrative Group

4.4. Traffic Engineering Metric

[RFC3630] defines Traffic Engineering Metric.

To advertise the Traffic Engineering Metric in the OSPFv2 Extended
Link TLV, the same format for the sub-TLV defined in section 2.5.5 of
[RFC3630] is used and TLV type TBD12 is used. Similarly, for OSPFv3
to advertise the Traffic Engineering Metric in the OSPFv3 Router-Link
TLV, TLV type TBD13 is used.

5. Maximum Link Bandwidth

Maximum link bandwidth is an application independent attribute of the
link that is defined in [RFC3630]. Because it is an application
independent attribute, it MUST NOT be advertised in ASLA sub-TLV.
Instead, it MAY be advertised as a sub-TLV of the Extended Link
Opaque LSA Extended Link TLV in OSPFv2 [RFC7684] or sub-TLV of OSPFv3
E-Router-LSA Router-Link TLV in OSPFv3 [RFC8362].

To advertise the Maximum link bandwidth in the OSPFv2 Extended Link
TLV, the same format for sub-TLV defined in [RFC3630] is used with
TLV type TBD23. TBD14.

To advertise the Maximum link bandwidth in the OSPFv3 Router-Link
TLV, the same format for sub-TLV defined in [RFC3630] is used with
TLV type TBD24.

7. TBD15.

6. Local Interface IPv6 Address Sub-TLV

The Local Interface IPv6 Address Sub-TLV is an application
independent attribute of the link that is defined in [RFC5329].
Because it is an application independent attribute, it MUST NOT be
advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a
sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362].

To advertise the Local Interface IPv6 Address Sub-TLV in the OSPFv3
Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is
used with TLV type TBD25.

8. TBD16.

7. Remote Interface IPv6 Address Sub-TLV

The Remote Interface IPv6 Address Sub-TLV is an application
independent attribute of the link that is defined in [RFC5329].
Because it is an application independent attribute, it MUST NOT be
advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a
sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362].

To advertise the Remote Interface IPv6 Address Sub-TLV in the OSPFv3
Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is
used with TLV type TBD26.

9. TBD17.

8. Deployment Considerations

If link attributes are advertised associated with zero length
application bit masks for both standard applications and user defined
applications, then that set of link attributes MAY be used by any
application. If support for a new application is introduced on any
node in a network in the presence of such advertisements, these
advertisements MAY be used by the new application. If this is not
what is intended, then existing advertisements MUST be readvertised
with an explicit set of applications specified before a new
application is introduced.

10.

9. Attribute Advertisements and Enablement

This document defines extensions to support the advertisement of
application specific link attributes.

Whether the presence of link attribute advertisements for a given
application indicates that the application is enabled on that link
depends upon the application. Similarly, whether the absence of link
attribute advertisements indicates that the application is not
enabled depends upon the application.

In the case of RSVP-TE, the advertisement of application specific
link attributes implies that RSVP is enabled on that link.

In the case of SRTE, advertisement of application specific link
attributes does NOT indicate enablement of SRTE. The advertisements
are only used to support constraints which may be applied when
specifying an explicit path. SRTE is implicitly enabled on all links
which are part of the Segment Routing enabled topology independent of
the existence of link attribute advertisements.

In the case of LFA, advertisement of application specific link
attributes does NOT indicate enablement of LFA on that link.
Enablement is controlled by local configuration.

In the case of Flexible Algorithm, advertisement of application
specific link attributes does NOT indicate enablement of Flexible
Algorithm on that link. Rather the attributes are used to determine
what links are included/excluded in the algorithm specific
constrained SPF. This is fully specified in
[I-D.ietf-lsr-flex-algo].

If, in the future, additional standard applications are defined to
use this mechanism, the specification defining this use MUST define
the relationship between application specific link attribute
advertisements and enablement for that application.

This document allows the advertisement of application specific link
attributes with no application identifiers i.e., both the Standard
Application Bit Mask and the User Defined Application Bit Mask are
not present (See Section 5. 3). This supports the use of the link
attribute by any application. In the presence of an application
where the advertisement of link attribute advertisements is used to
infer the enablement of an application on that link (e.g., RSVP-TE),
the absence of the application identifier leaves ambiguous whether
that application is enabled on such a link. This needs to be
considered when making use of the "any application" encoding.

11.

10. Backward Compatibility

Link attributes may be concurrently advertised in both the TE Opaque
LSA and the Extended Link Opaque LSA in OSPFv2 and the OSPFv3 Intra-
Area-TE-LSA and OSPFv3 Extended LSA Router-Link TLV in OSPFv3.

In fact, there is at least one OSPF implementation that utilizes the
link attributes advertised in TE Opaque LSAs [RFC3630] for Non-RSVP
TE applications. For example, this implementation of LFA and remote
LFA utilizes links attributes such as Shared Risk Link Groups (SRLG)
[RFC4203] and Admin Group [[RFC3630] advertised in TE Opaque LSAs.
These applications are described in [RFC5286], [RFC7490], [RFC7916]
and [RFC8102].

When an OSPF routing domain includes routers using link attributes
from the OSPFv2 TE Opaque LSAs or the OSPFv3 Intra-Area-TE-LSA for
Non-RSVP TE applications such as LFA, OSPF routers in that domain
SHOULD continue to advertise such OSPFv2 TE Opaque LSAs or the OSPFv3
Intra-Area-TE-LSA. If there are also OSPF routers using the link
attributes described herein for any other application, OSPF routers
in the routing domain will also need to advertise these attributes in
OSPFv2 Extended Link Attributes LSAs or OSPFv3 E-Router-LSA. In such
a deployment, the advertised attributes SHOULD be the same and Non-
RSVP application access to link attributes is a matter of local
policy.

12.

11. Security Considerations

Existing security extensions as described in [RFC2328], [RFC5340] and
[RFC8362] apply to extensions defined in this document. While OSPF
is under a single administrative domain, there can be deployments
where potential attackers have access to one or more networks in the
OSPF routing domain. In these deployments, stronger authentication
mechanisms such as those specified in [RFC5709], [RFC7474], [RFC4552]
or [RFC7166] SHOULD be used.

Implementations must MUST assure that malformed TLV and Sub-TLV
permutations defined in
this document are detected and do not result in errors that cause hard provide a vulnerability for
attackers to crash the OSPF failures.

13. router or routing process. Reception of
a malformed TLV or Sub-TLV SHOULD be counted and/or logged for
further analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be
rate-limited to prevent a Denial of Service (DoS) attack (distributed
or otherwise) from overloading the OSPF control plane.

12. IANA Considerations

13.1.

12.1. OSPFv2

OSPFv2 Extended Link TLV Sub-TLVs registry [RFC7684] defines sub-TLVs
at any level of nesting for OSPFv2 Extended Link TLVs. This
specification updates OSPFv2 Extended Link TLV sub-TLVs registry with
the following TLV types:

TBD21 (10 Recommended)

10 - Application Specific Link Attributes

TBD1 (11 Recommended)

11 - Shared Risk Link Group

TBD3 (12 Recommended)

12 - Unidirectional Link Delay

TBD4 (13 Recommended)

13 - Min/Max Unidirectional Link Delay
TBD5 (14 Recommended)

14 - Unidirectional Delay Variation

TBD6 (15 Recommended)

15 - Unidirectional Link Loss

TBD7 (16 Recommended)

16 - Unidirectional Residual Bandwidth

TBD8 (17 Recommended)

17 - Unidirectional Available Bandwidth

TBD9 (18 Recommended)

18 - Unidirectional Utilized Bandwidth

TBD9 (19 Recommended)

19 - Administrative Group

TBD17 (20 Recommended)

20 - Extended Administrative Group

TBD23 (21 Recommended) - Maximum Link Bandwidth

TBD27

TBD12 (22 Recommended) - Traffic Engineering Metric

13.2.

TBD14 (21 Recommended) - Maximum Link Bandwidth

12.2. OSPFv3

OSPFv3 Extended LSA Sub-TLV Registry [RFC8362] defines sub-TLVs at
any level of nesting for OSPFv3 Extended LSAs. This specification
updates OSPFv3 Extended LSA Sub-TLV Registry with the following TLV
types:

TBD22 (9

TBD1 (10 Recommended) - Application Specific Link Attributes

TBD2 (10 (11 Recommended) - Shared Risk Link Group

TBD10 (11

TBD3 (12 Recommended) - Unidirectional Link Delay

TBD11 (12

TBD4 (13 Recommended) - Min/Max Unidirectional Link Delay

TBD12 (13

TBD5 (14 Recommended) - Unidirectional Delay Variation

TBD13 (14

TBD6 (15 Recommended) - Unidirectional Link Loss

TBD14 (15

TBD7 (16 Recommended) - Unidirectional Residual Bandwidth

TBD15 (16

TBD8 (17 Recommended) - Unidirectional Available Bandwidth

TBD16 (17

TBD9 (18 Recommended) - Unidirectional Utilized Bandwidth

TBD19 (18

TBD10 (19 Recommended) - Administrative Group

TBD20 (19

TBD11 (20 Recommended) - Extended Administrative Group

TBD24 (20

TBD13 (21 Recommended) - Traffic Engineering Metric

TBD15 (22 Recommended) - Maximum Link Bandwidth
TBD25 (21

TBD16 (23 Recommended) - Local Interface IPv6 Address Sub-TLV

TBD26 (22

TBD17 (24 Recommended) - Local Interface IPv6 Address Sub-TLV

TBD28 (23 Recommended) - Traffic Engineering Metric

13. Contributors

The following people contributed to the content of this document and
should be considered as co-authors:

Acee Lindem
Cisco Systems
301 Midenhall Way
Cary, NC 27513
USA

Email: acee@cisco.com

Ketan Talaulikar
Cisco Systems, Inc.
India

Email: ketant@cisco.com

Hannes Gredler
RtBrick Inc.
Austria

Email: hannes@rtbrick.com

14. Acknowledgments

Thanks to Chris Bowers for his review and comments.

15. References

15.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC3630, September 2003,
<https://www.rfc-editor.org/info/rfc3630>.

[RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
"Traffic Engineering Extensions to OSPF Version 3",
RFC 5329, DOI 10.17487/RFC5329, September 2008,
<https://www.rfc-editor.org/info/rfc5329>.

[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.

[RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework",
RFC 5714, DOI 10.17487/RFC5714, January 2010,
<https://www.rfc-editor.org/info/rfc5714>.

[RFC7308] Osborne, E., "Extended Administrative Groups in MPLS
Traffic Engineering (MPLS-TE)", RFC 7308,
DOI 10.17487/RFC7308, July 2014,
<https://www.rfc-editor.org/info/rfc7308>.

[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <https://www.rfc-editor.org/info/rfc7684>.

[RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and
F. Baker, "OSPFv3 Link State Advertisement (LSA)
Extensibility", RFC 8362, DOI 10.17487/RFC8362, April
2018, <https://www.rfc-editor.org/info/rfc8362>.

15.2. Informative References

[I-D.ietf-idr-ls-distribution]
Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
Ray, "North-Bound Distribution of Link-State and TE
Information using BGP", draft-ietf-idr-ls-distribution-13
(work in progress), October 2015.

[I-D.ietf-isis-te-app]
Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and
J. Drake, "IS-IS TE Attributes per application", draft-
ietf-isis-te-app-05
ietf-isis-te-app-06 (work in progress), October 2018. April 2019.

[I-D.ietf-lsr-flex-algo]
Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
algo-00 (work in progress), May 2018.

[I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-25
algo-01 (work in progress), April November 2018.

[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.

[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
<https://www.rfc-editor.org/info/rfc4203>.

[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
<https://www.rfc-editor.org/info/rfc4552>.

[RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for
IP Fast Reroute: Loop-Free Alternates", RFC 5286,
DOI 10.17487/RFC5286, September 2008,
<https://www.rfc-editor.org/info/rfc5286>.

[RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
Authentication", RFC 5709, DOI 10.17487/RFC5709, October
2009, <https://www.rfc-editor.org/info/rfc5709>.

[RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework",
RFC 5714, DOI 10.17487/RFC5714, January 2010,
<https://www.rfc-editor.org/info/rfc5714>.

[RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting
Authentication Trailer for OSPFv3", RFC 7166,
DOI 10.17487/RFC7166, March 2014,
<https://www.rfc-editor.org/info/rfc7166>.

[RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S.
Previdi, "OSPF Traffic Engineering (TE) Metric
Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015,
<https://www.rfc-editor.org/info/rfc7471>.

[RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
"Security Extension for OSPFv2 When Using Manual Key
Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
<https://www.rfc-editor.org/info/rfc7474>.

[RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N.
So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)",
RFC 7490, DOI 10.17487/RFC7490, April 2015,
<https://www.rfc-editor.org/info/rfc7490>.

[RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,
Litkowski, S., Horneffer, M., and R. Shakir, "Source
Packet Routing in Networking (SPRING) Problem Statement
and Requirements", RFC 7855, DOI 10.17487/RFC7855, May
2016, <https://www.rfc-editor.org/info/rfc7855>.

[RFC7916] Litkowski, S., Ed., Decraene, B., Filsfils, C., Raza, K.,
Horneffer, M., and P. Sarkar, "Operational Management of
Loop-Free Alternates", RFC 7916, DOI 10.17487/RFC7916,
July 2016, <https://www.rfc-editor.org/info/rfc7916>.

[RFC8102] Sarkar, P., Ed., Hegde, S., Bowers, C., Gredler, H., and
S. Litkowski, "Remote-LFA Node Protection and
Manageability", RFC 8102, DOI 10.17487/RFC8102, March
2017, <https://www.rfc-editor.org/info/rfc8102>.

[RFC8379] Hegde, S., Sarkar, P., Gredler, H., Nanduri, M., and L.
Jalil, "OSPF Graceful Link Shutdown", RFC 8379,
DOI 10.17487/RFC8379, May 2018,
<https://www.rfc-editor.org/info/rfc8379>.

Authors' Addresses

Peter Psenak (editor)
Cisco Systems, Inc. Systems
Eurovea Centre, Central 3
Pribinova Street 10
Bratislava 81109
Slovakia

Email: ppsenak@cisco.com

Acee Lindem
Cisco Systems
301 Midenhall Way
Cary, NC 27513
USA

Email: acee@cisco.com

Les Ginsberg
Cisco Systems
821 Alder Drive
MILPITAS, CA 95035
USA

Email: ginsberg@cisco.com

Wim Henderickx
Nokia
Copernicuslaan 50
Antwerp, 2018 94089
Belgium

Email: wim.henderickx@nokia.com

Jeff Tantsura
Nuage Networks
Apstra
US

Email: jefftant.ietf@gmail.com

Hannes Gredler
RtBrick Inc.

Email: hannes@rtbrick.com

John Drake
Juniper Networks
1194 N. Mathilda Ave
Sunnyvale, California 94089
USA

Email: jdrake@juniper.net